It is desirable to trap evaporated fuel and oil vapors within the air intake system, thereby preventing their release into the outside environment. Fuel vapors contain hydrocarbons which are known to be a significant contributing component in urban smog.
Gasoline, for example, is a highly volatile hydrocarbon fuel that includes components which transition easily from a liquid to vapor phase. Elevated temperatures such as occurring during normal internal combustion engine operation accelerate the liquid to vapor transition. The hydrocarbon vapors, unless treated or captured, may ultimately discharge into the atmosphere. It is known that hydrocarbon vapors are discharged from the engine crankcase during engine operation. When the engine is shutdown, these vapors may continue to be released from the hot engine crankcase and other components, particularly as the engine cools.
The control of hydrocarbon vapors escaping into the environment is regulated by state and federal regulations. Hydrocarbon traps for capturing hydrocarbon vapors are well known. For example, motor vehicles are commonly equipped with hydrocarbon adsorptive emissions canisters connected to the fuel tank for trapping hydrocarbon vapors, particularly as emitted during refueling.
It is known that certain porous materials such as activated carbon are useful for absorption and removal of organic hydrocarbon vapors. It is known hydrocarbon vapors are liquefied within small micro pores of the activated carbon and may be retained by absorption.
Various types of hydrocarbon traps for capturing hydrocarbon vapors are known in the art. For example, U.S. Pat. No. 5,914,294 discloses a monolithic trap which adsorbs chemical constituents from a gas stream. This is achieved by bringing the gas into direct contact with the activated carbon in the monolith. One disadvantage of this type of extruded or press formed hydrocarbon trap is that the extrusion and binding process results in a relatively brittle trap that may crack or have individual pieces flake off.
Another example is U.S. Published Application 2005/0223894 which discloses an adsorption element for adsorbing gases and vapors from the intake tract of an engine. The adsorption element has free-flow channels in an element having a spacer layer and an adsorption layer. One disadvantage of this type of corrugated trap is that the trap itself introduces a restriction to airflow in the intake tract.
Therefore, there remains a need in the art for a hydrocarbon adsorption trap that is rugged, low in cost, and does not present a restriction to air flow in the air intake tract.